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TYPE Brief Research Report
PUBLISHED 02 November 2022
DOI 10.3389/fspor.2022.966203
OPEN ACCESS
EDITED BY
Gustavo R. Mota,
Federal University of Triângulo
Mineiro, Brazil
REVIEWED BY
Tobias Dünnwald,
Medical Informatics and Technology
(UMIT), Austria
Andreas Breenfeldt Andersen,
University of Copenhagen, Denmark
*CORRESPONDENCE
Thomas Blokker
thomas.blokker@baspo.admin.ch
†These authors share last authorship
SPECIALTY SECTION
This article was submitted to
Elite Sports and Performance
Enhancement,
a section of the journal
Frontiers in Sports and Active Living
RECEIVED 10 June 2022
ACCEPTED 07 October 2022
PUBLISHED 02 November 2022
CITATION
Blokker T, Bucher E, Steiner T and
Wehrlin JP (2022) Eect of cold
ambient temperature on heat flux, skin
temperature, and thermal sensation at
dierent body parts in elite biathletes.
Front. Sports Act. Living 4:966203.
doi: 10.3389/fspor.2022.966203
COPYRIGHT
©2022 Blokker, Bucher, Steiner and
Wehrlin. This is an open-access article
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(CC BY). The use, distribution or
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practice. No use, distribution or
reproduction is permitted which does
not comply with these terms.
Eect of cold ambient
temperature on heat flux, skin
temperature, and thermal
sensation at dierent body parts
in elite biathletes
Thomas Blokker *, Elias Bucher , Thomas Steiner †and
Jon Peter Wehrlin †
Section for Elite Sport, Swiss Federal Institute of Sport, Magglingen, Switzerland
Introduction: When exercising in the cold, optimizing thermoregulation is
essential to maintain performance. However, no study has investigated thermal
parameters with wearable-based measurements in a field setting among elite
Nordic skiers. Therefore, this study aimed to assess the thermal response
and sensation measured at dierent body parts during exercise in a cold
environment in biathletes.
Methods: Thirteen Swiss national team biathletes (6 females, 7 males)
performed two skiing bouts in the skating technique on two consecutive days
(ambient temperature: −3.74 ±2.32 ◦C) at 78 ±4% of maximal heart rate. Heat
flux (HF), core (Tcore) and skin (Tskin ) temperature were measured with sensors
placed on the thigh, back, anterior and lateral thorax. Thermal sensation (TS)
was assessed three times for dierent body parts: in protective winter clothing,
in a race suit before (PRE) and after exercise (POST).
Results: HF demonstrated dierences (p<0.001) between sensor locations,
with the thigh showing the highest heat loss (344 ±37 kJ/m2), followed by
the back (269 ±6 kJ/m2), the lateral thorax (220 ±47 kJ/m2), and the anterior
thorax (192 ±37 kJ/m2). Tcore increased (p<0.001). Tskin decreased for all
body parts (p<0.001). Thigh Tskin decreased more than for other body parts
(p<0.001). From PRE to POST, TS of the hands decreased (p<0.01).
Conclusion: Biathletes skiing in a race suit at moderate intensity experience
significant heat loss and a large drop in Tskin, particularly at the quadriceps
muscle. To support the optimal functioning of working muscles, body-part
dependent dierences in the thermal response should be considered for
clothing strategy and for race suit design.
KEYWORDS
cross-country skiing, cold stress, thermoregulation, skin temperature, heat flux, heat
loss, field measurement
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Blokker et al. 10.3389/fspor.2022.966203
Introduction
Endurance performance is well known to depend on the
external environmental conditions, particularly temperature, as
well as the suitability of the clothing worn correspondingly
(1–3). Indeed, a small rise or drop in core temperature
(Tcore) can lead to a decrease in oxygen uptake ( ˙
VO2),
aerobic power and muscle force production (4–6). While
the causing mechanisms limiting aerobic exercise in the heat
are complex but seem to be relatively clear (7), the ones
impacting performance inherent to the cold have not received
as much research attention (6). In a summary review, the
latter authors have suggested possible mechanisms that impact
˙
VO2and aerobic performance in a cold environment. Namely
changes in: temperature (lower deep body, muscle and skin
temperature); metabolism (increased lactate, low glucose, fasting
and increased ˙
VO2/reduced economy); and central/peripheral
circulation (reduced maximal heart rate, lower cardiac output
and reduced muscle blood flow) (6). Although the individual
extent to which each of these mechanisms impairs performance
is not fully understood, a decrease in the different physiological
temperatures seem to affect endurance exercise capacity
(4,8). Skin temperature (Tskin) appears to be particularly
important, as a larger gradient between Tcore and Tskin is
indicative of a higher heat loss. Despite a stable elevated
Tcore, heat loss from a drop of mean Tskin to 27.2 ◦C is
more than twofold compared to resting conditions (1,9).
Therefore, keeping the Tskin of working muscles above a
critical level can pose a challenge in biathlon and cross-country
skiing, where ambient temperatures can drop to −20 ◦C
during competition.
It has been demonstrated that subzero temperatures impair
endurance performance, ˙
VO2and exercise economy in cross-
country skiers (3,10–12). When performing at maximal
intensity in a cold environment, Tskin decreases proportionally
to the severity of the cold ambient temperature, although Tcore
increases (3). The authors, therefore, suggest that a possible
responsible mechanism for the diminished performance could
be the lower Tskin, which likely induces a decrease in muscle
temperature (Tmuscle). Hence, preventing a drop in Tskin
appears relevant. Dry and evaporative heat loss may be mitigated
with clothing, which provides a barrier for heat transfer between
the skin and the environment (13). However, as cutaneous
blood flow fluctuates across body regions, so does Tskin (14).
Accordingly, gaining knowledge in terms of where in the body
the most substantial decrease in Tskin, and thus heat loss occurs,
appears relevant to optimize clothing strategies (15). To improve
skiing performance in the cold, relevant muscle groups should
be appropriately covered to allow for optimal thermoregulation.
However, there is a lack of research examining the thermal
response to the cold of different body parts of elite biathletes in a
field setting. Moreover, whether the physiological measurements
diverge from the subjective thermal sensation (TS) experienced
by athletes in the cold is also unknown.
Therefore, the purpose of the present brief report was to
assess the thermal response of elite biathletes to a cross-country
skiing bout in a cold environment in a standard racing suit.
Specifically, the aim was to monitor the Tskin, Tcore and heat
flux (HF) development in a field setting with a race suit, and
identify possible differences between body parts. A second aim
was to assess the subjective thermal sensation for relevant body
parts over the course of the exercise session.
Materials and methods
Study design and participants
Thirteen national team biathletes (6 females and 7 males;
age: 27 ±4 years) performed an exercise protocol consisting
of two cross-country skiing bouts on two consecutive days.
HF, Tcore and Tskin were measured continuously with sensors
placed on different body parts, and TS was assessed before
and after the bouts for different locations on the body.
Anthropometrics, maximal oxygen uptake ( ˙
VO2max), aerobic
and anaerobic thresholds (Table 1) were determined 7–14 days
before the field tests in the laboratory of the Swiss Federal
Institute of Sport Magglingen (SFISM). All participants provided
informed consent to participate in this study in accordance with
the internal review board of the SFISM and the Declaration
of Helsinki.
Exercise protocol
The cross-country skiing bouts (men: 4.12 km; women:
3.49 km) lasted 14.3 ±1.3 min, and were performed in the
skating technique at an intensity of 78 ±4% of their maximal
heart rate based on the information from the graded exercise
test (GXT) (details below). Starting at 717 m above sea level,
the ski track consisted of six uphill, six downhill and seven flat
sections, crossing the low point at 698 m and the high point at
735 m above sea level. The ambient temperature and relative
humidity were −1.7 ±0.6 ◦C and 88.6 ±5.3% for day 1, and
−6.0 ±0.7 ◦C and 97.4 ±3.5% for day 2, respectively. The skiing
bouts were performed at the same time of the day for both days.
The participants’ heart rate was continuously monitored with a
chest heart rate monitor (HRM-Pro, Garmin, Olathe, KS, USA)
and displayed on a wristwatch (Forerunner 35, Garmin, Olathe,
KS, USA). The participants were instructed to adapt the skiing
velocity in accordance with the exercise intensity prescription
at a target heart rate corresponding to their aerobic threshold
(AeT), defined in the GXT.
Athletes performed the skiing bout twice, as environmental
conditions for races throughout the season change significantly
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TABLE 1 Anthropometric and performance characteristics.
Females Males
n 6 7
Age (y) 25.6 ±3.9 28.2 ±4.6
Body height (cm) 166.4 ±7.0 180.1 ±3.1
Body mass (kg) 62.5 ±9.0 75.7 ±6.5
Body fat (%) 22.5 ±4.1 11.4 ±1.8
˙
VO2max (ml·kg−1·min−1) 59.8 ±3.7 69.7 ±3.7
GXT AeT HR (bpm) 157 ±8 143 ±5
GXT AnT HR (bpm) 185 ±6 176 ±5
˙
VO2max, maximal oxygen consumption; GXT, graded exercise test; AeT, aerobic
threshold; AnT, anaerobic threshold; HR, heart rate.
Mean ±SD.
and individual preferences vary greatly as to which layers are
worn underneath the racing suit. As a result, athletes were
explicitly instructed to pursue two clothing strategies simulating
a race in warm conditions (i.e., which generally consists
of underwear, socks, short base layer, race suit, headband
and gloves) and cold conditions (i.e., underwear, socks, long
underwear, long upper-body base layer, race suit, neck warmer,
beanie and gloves), randomly assigned to the first and second
days. They completed a crossover on the alternative day. The
mean of the individual measurements from both days was
used for further analysis. Athletes used their own skating
cross-country ski equipment with standardized base wax for
both days.
Tskin as well as HF were recorded at 1 Hz throughout the
entire skiing bout, with wearable non-invasive sensors (CORE,
greenTEG AG, Zurich, Switzerland) positioned directly on the
skin: (I) in the middle of the vastus lateralis (thigh), (II) 2 cm
above the spinous process of the T12 vertebra (back), (III)
on the sternum (anterior thorax) and (IV) 20 cm under the
arm pit (lateral thorax) and were held in place with a custom-
made elastic Velcro-strap. Tcore was computed with a machine-
learning algorithm (greenTEG AG, Zurich, Switzerland). The
calculations were derived from both the heart rate measurement
as well as the HF and Tskin data from the lateral thorax
CORE sensor. For inter-test reproducibility purposes, the exact
positions of the sensors were marked with a permanent pen.
In order to avoid interference with the sensor measurements
placed on the back, athletes were not wearing their rifles. For
each body part, the total heat loss for the entire exercise was
defined as the total area under the curve from the start to
the end of the skiing bout. For Tcore and Tskin, the reference
value (START) was the average of the five values before and
the five values after the start of the exercise (resulting in a 10 s
average around the start time), whereas the end of the exercise
(END) value was the average of the last 2 min of the skiing
bout. Athletes were equipped with the sensors indoors at room
temperature conditions (temperature 19.9 ±1.0 ◦C, relative
humidity 26.8 ±7.8%) for a 10-min baseline measurement
and to avoid premature cold exposure. Upon completion of
the indoor baseline measurement, the athletes left the building
and proceeded to the adjacent ski track. The subjective TS was
assessed for the torso, arms, hands, legs, feet, head, neck and
whole body via an adapted seven-point scale from −3 (cold) to
3 (hot) (16), in protective winter clothing (REF), as well as right
before (PRE) and after (POST) the exercise bout in the respective
race suit.
Anthropometrics and laboratory tests
Body fat content was determined using dual-energy X-ray
absorptiometry (Lunar iDXA, GE Medical Systems, Chicago,
IL, USA). ˙
VO2max was determined with the Douglas Bag
technique using an uphill running test protocol to task failure
on a motorized treadmill (17).
The first lactate threshold and the lactate turning point
were determined during a GXT using a sport-specific treadmill
protocol on rollerskis in the skating technique. At a starting
velocity of 2.50 m·s−1and an incline of 1, 2 or 3◦based
on the athlete’s performance level, skiers completed recurring
5-min stages interspersed by 1 min of passive re covery. The
workload was increased stepwise by a 1◦incline. Heart rate
was continuously measured (Firstbeat Technologies, Jyväskylä,
Finland), and earlobe capillary blood samples were taken at the
end of each stage to determine blood lactate concentration. The
first (GXT AeT) and second (GXT AnT) lactate thresholds were
calculated using the modified Dmod method (18). The heart rate
associated with the GXT AeT was used as the target intensity
during the field exercise in the cold, which corresponded to 78
±4% of subjects’ maximal heart rate.
Statistical analysis
Unless specified otherwise, all data are presented as mean
±SD. For the total heat losses, the areas under the HF
curves were calculated following a numerical integration using
Simpson’s Rule (19). Normal distribution was checked with the
Shapiro–Wilk test. Differences in HF were evaluated with a
one-way analysis of variance (ANOVA). Changes in Tcore were
evaluated with the Wilcoxon signed-rank test. Differences in
Tskin, as well as in TS were assessed using a two-way repeated
measure ANOVA (time x body part). In the case of significant
main effects, pairwise post hoc Tukey’s multiple comparisons
of means were applied. The effect size was measured with
partial eta squared (ηp²). The significance level was set at p
<0.05 for all analyses. All statistics were performed using R
Studio (20).
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Results
Heat flux
HF increased for all body parts with the onset of
exercise and rapidly decreased after the end of the
skiing bout (Figure 1). Heat losses during exercise were
different between body parts [F(3, 12) =55.01, p<
0.0001, ηp²=0.82]. Heat loss for the thigh (344 ±
37 kJ/m2) was higher (p<0.01) than for all other
body parts, while heat loss on the back (269 ±56
kJ/m2) was higher than on the lateral thorax (220 ±
47 kJ/m2) and the anterior thorax (192 ±37 kJ/m2).
Lateral and anterior thorax did not differ in heat
loss (p=0.14).
Core and skin temperature
From the start of the skiing bout to the end, Tcore
slightly increased from 37.0 ±0.2 ◦C to 37.5 ±0.2 ◦C
(p<0.001) (Figure 2A). Tskin at START were 30.4 ±0.9
◦C, 32.9 ±0.9 ◦C, 33.4 ±1.3 ◦C, and 33.8 ±0.7 ◦C
for the thigh, back, anterior and lateral thorax, respectively.
Throughout the exercise, Tskin decreased for all body parts
[F(1, 12) =251.5, p<0.0001, ηp²=0.95] to 22.9 ±
1.6 ◦C, 30.2 ±1.2 ◦C, 29.0 ±3.2 ◦C, and 31.3 ±1.6 ◦C,
for the thigh, back, anterior and lateral thorax, respectively
(Figure 2B). Tskin at the thigh was lower (p<0.001) than
other body parts at START and END, while Tskin for the lateral
thorax was higher (p< 0.001) than for the anterior thorax
at END.
FIGURE 1
Mean heat flux measured at dierent body parts before, during
and after exercise. Dashed lines mark the start and the end of
the skiing bout.
FIGURE 2
Mean core (A) and skin (B) temperature at dierent body parts
before, during and after exercise. Dashed lines mark the start
and end of the skiing bout.
Subjective thermal sensation
The TS results are summarized in Table 2. The TS for
the hands was the only one that dropped significantly from
PRE to POST. A greater intersubject variability identifiable by
larger standard deviations at PRE and POST was observed in
comparison to REF.
Neither the physiological measurements nor the TS across
body parts demonstrated a significant difference between the
two clothing conditions and the two test days (all p>0.05).
Discussion
The purpose of this study was to assess the thermal response
of elite biathletes to a cross-country skiing bout at moderate
intensity in a cold environment. This is the first study reporting
HF, Tskin and TS measured concurrently in a field setting. The
principal finding is a large decrease in Tskin and an increase in
HF for all body parts, particularly for the quadriceps muscle,
despite a moderate increase in Tcore. A second novel finding is
that TS does not necessarily match the measured heat loss or
Tskin at different body parts.
Our findings suggest that during cross-country skiing in the
cold, the elevation in heat transfer that occurs is primarily driven
by a large drop in Tskin. They also corroborate analogous results
conveying that Tskin is more dependent on ambient temperature
than on Tcore (2,21). Presently, the number of sensors used
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TABLE 2 Mean thermal sensation from an analog seven-point scale
according to body parts.
Body part REF PRE POST
Whole body 1.03 ±0.87 −0.15 ±1.41*** 0.12 ±1.24***
Legs 0.88 ±1.07 −0.26 ±1.37*** −0.44 ±1.40***
Hands 0.15 ±1.26 0.51 ±0.90 −0.53 ±1.83##
Feet 0.70 ±1.17 0.53 ±1.36 0.06 ±1.52*
Arms 0.81 ±1.10 −0.72 ±1.21*** −0.23 ±1.16**
Chest 1.34 ±0.75 0.27 ±1.25*** 0.50 ±1.02***
Head 0.95 ±0.88 0.42 ±1.24* −0.11 ±1.65***
Neck 0.89 ±0.99 0.23 ±1.21* 0.15 ±1.38*
Expressed in arbitrary units from −3 (cold) to +3 (warm). Mean ±SD.
***p<0.001, ** p<0.01, *p<0.05 indicate a significant difference from REF, ##p<0.01
indicates a significant difference from PRE.
is not enough to be aggregated into a mean skin temperature
(22). However, the decrease in Tskin observed for every given
body part in spite of a raised Tcore is aligned with similar
studies that also measured a Tskin drop in all measurement
locations following a cross-country skiing exercise in the cold
(3,11,23). This drop in Tskin seems relevant, as it has been
linked to decreased cross-country skiing performance, which
was suggested to be due to a lower muscle temperature (3). As
it has been shown that vasoconstriction is maximal when Tskin
is lower than 31◦C (24), at which point a decline in peripheral
tissue temperature occurs (25), a lower muscle temperature can
be assumed. In our case, with POST Tskin dropping below 31◦C
for the thigh, back and anterior thorax, it is probable that the
subcutaneous muscle tissues underneath also suffered from a
drop in temperature or at least from a reduced increase in
temperature in the working muscle. It is well documented that a
reduced muscle temperature influences performance negatively
(4,8,26). Moreover, it has been shown that during moderate-
intensity exercise in the cold where Tskin is reduced, muscle
temperature increases to a lesser extent than during the same
exercise intensity in warmer conditions (27–29). While the exact
influence of Tskin on muscle temperature is not entirely clear,
it can be assumed that muscle temperature is influenced by the
proximity of the muscle tissue to the skin surface, especially in
smaller, peripheral muscle groups.
The locations exhibiting the largest decrease in Tskin (thigh
and anterior thorax) are located on the front surface of the
body exposed to an intensified effect of convective heat transfer
due to the skiing velocity. It has already been shown that Tskin
measurements on the front of the body are lower than Tskin
measurements on the back of the body when moving at a fast
velocity or against a headwind (23,30). The severity of the
decrease in Tskin for the thigh may be explained by the tight fit of
the race suit layer on the skin, getting temporarily thinner with
the flexion of the knees during the skating motion. Additionally,
it can be assumed that the thigh loses more heat due to being an
extremity and thus prone to a higher surface area to mass ratio.
HF appears to be strongly related to the activation and size
of the underlying muscle groups and the Tskin at the specific
body part, since muscle activation increases metabolic heat
production, thereby leading to a higher temperature gradient
between the musculature and the skin and hence to a higher heat
loss (1). Indeed, out of the four sensor locations, the ones placed
on the thigh and the back, above muscle groups majorly involved
in the cross-country skiing propulsion movement, showed the
largest increase in HF. Muscle heat production and Tcore in
the cold are essentially subject to exercise intensity (31) and
cannot be easily regulated. Accordingly, at moderate intensity,
preventing an incline in skin cooling is paramount and seems
to be the most effective approach to reduce the peripheral-to-
core temperature gradient and thus heat loss. As the HF increase
and Tskin decrease were not uniform between body parts in the
present study, the anterior/posterior and the upper body-lower
body differences in heat loss should be taken into account in the
development of ski-race suits.
Interestingly, the TS did not necessarily match the measured
heat loss or Tskin at the different body parts. Indeed, although a
drastic and significant decrease in both heat loss and Tskin could
be measured for the legs, from PRE to POST the TS for this
body part only slightly decreased from −0.26 ±1.37 to −0.44
±1.40 on the −3 to +3 TS scale. Similarly, Tskin for the anterior
thorax was significantly reduced during the cross-country skiing
bout, whereas from PRE to POST, TS for that region slightly
increased. Although there is a general trend toward lower
values and thus a colder subjective sensation, from both REF
to PRE, and from PRE to POST, only the hands were perceived
as significantly colder after the skiing bout. Nevertheless, we
observed a large inter-individual variation in both total heat
loss and TS at PRE, and POST particularly, confirming a non-
negligible wide inter-individual variability in thermal response
to a set environment and work load (32). Possible explanations
include body composition, sex and morphology (i.e., surface
area to mass ratio) (6). The areas of the body that were perceived
as the coldest at POST tended to be in the periphery, while body
parts closer to the core (i.e., trunk), were sensed as warmer. This
discrepancy between physiological parameters and subjective
sensation is in line with other studies reporting that exercise
blunts cutaneous TS in the cold (33,34). These results may be
problematic, as they attests that athletes’ sensations may not
accurately mirror Tskin and heat loss development. Therefore,
athletes may not dress accordingly. As a result, biathletes and
cross-country skiers may have to anticipate more physiological
thermal stress than the one their subjective feelings may portray.
Limitations
It should be considered that our results may have been
affected by some limitations. First, in contrast to a climatic
chamber, environmental conditions can vary substantially
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Blokker et al. 10.3389/fspor.2022.966203
throughout the day and between days in the field. Tskin
has been shown to be dependent on ambient temperature
(21). Therefore, any possible variation of ambient temperature
during the day may have induced inter-individual differences in
Tskin. Second, subjects could not self-select clothing based on
environmental conditions and were potentially dressed either
too warm or too cold. This may have influenced each subject’s
physiological thermal response and TS. However, this effect
was mitigated by randomly allocating subjects to either type
of outfit and executing a crossover the next day. On the
same note, women wore thorax sensors under their sports
bra, which may have induced a systematic bias by creating
more insulation for these three sensors. Additionally, HF and
Tskin for the head, which was shown to demonstrate the
lowest Tskin value in cross-country skiing in the cold (23),
was not evaluated here, as only four CORE sensors per person
were available. Athletes performed the measurements at a
submaximal moderate intensity, which is below the intensity
they would normally ski during a race. Higher intensity exercise
requires greater muscle activation; thus, generating additional
heat. Therefore, different responses in HF, Tcore and Tskin than
measured in the present study are likely. Finally, the effect of the
cold on shooting performance was not investigated. As standing
passive time during shooting can vary greatly, this would have
represented another uncontrollable influencing factor on the
overall thermoregulatory development, which is why only the
skiing part was examined.
Practical application
This study provides novel insights into the thermal response
of elite biathletes during a moderate-intensity cross-country
skiing bout in the cold, with potential guidance regarding
clothing strategies for skiing performance. Given our results,
avoiding an excessive drop in Tskin is vital to prevent heat
loss. Accordingly, a clothing system specifically targeting the
extremities, and in particular the frontal areas where large
muscle groups are involved in locomotion, seems like an
appropriate strategy to minimize a decrease in Tskin and
to minimize heat loss in temperatures well below zero.
Possible concepts may include creating a thickness gradient
from the front to the back, wearing more lower-body base
layers, or wearing battery-based heated gloves to prevent cold
hands. Keeping the thigh muscles warm before the start with
appropriate insulating trousers to prevent premature cooling
down of Tskin seems to be an additional important aspect.
Further research on the thermal response in biathletes is still
needed, particularly on the effect of the cold on Tmuscle during
cross-country skiing, on the effect of the shooting portion and
the effect of skiing at race intensity.
Data availability statement
The raw data supporting the conclusions of this article will
be made available by the authors, without undue reservation.
Ethics statement
Ethical review and approval was provided by the Internal
Review Board of the Swiss Federal Institute of Sport Magglingen,
in accordance with the institutional requirements. Written
informed consent to participate in this study was provided by
all subjects.
Author contributions
EB and TS designed the study. TB, EB, and TS collected
the data and performed the data analysis. TB, EB, TS, and JW
interpreted the data and critically revised the paper. TB drafted
the paper. All authors gave final approval for publication and
agree to be held accountable for the work performed therein.
Funding
This study was funded by Swiss Olympic and the Swiss
Federal Institute of Sport Magglingen in Switzerland in
collaboration with the Swiss-Ski Biathlon Federation.
Acknowledgments
The authors thank the Swiss-Ski Biathlon Federation, the
national coaches and the participating athletes for their time and
efforts during the experiment.
Conflict of interest
The authors declare that the research was conducted in the
absence of any commercial or financial relationships that could
be construed as a potential conflict of interest.
Publisher’s note
All claims expressed in this article are solely those of the
authors and do not necessarily represent those of their affiliated
organizations, or those of the publisher, the editors and the
reviewers. Any product that may be evaluated in this article, or
claim that may be made by its manufacturer, is not guaranteed
or endorsed by the publisher.
Frontiers in Sports and Active Living 06 frontiersin.org
Blokker et al. 10.3389/fspor.2022.966203
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